Fluid-dynamic press for the cold forming of sheet metal

ABSTRACT

A fluid-dynamic press, in particular a hydraulic press, for the cold forming of sheet metal of thin thickness wherein the pressure application means acts directly upon the work piece, comprising a means for providing a packing on the pressure side of the work piece positioned to cooperate with an annular holding plate associated with a plurality of hydraulic clamping pistons on the opposite side of the workpiece, said holding plate and hydraulic clamping pistons being mounted in a removable die body mounted in the press and an integral part of the die. Consequently, the workpiece holding means and sealing means are specifically designed to fit each die body employed.

Blanchi FLUID-DYNAMIC PRESS FOR THE COLD FORMING OF SHEET METAL [75] Inventor: Turreno Blanchi, Terni, Italy [73] Assignee: S.A.I.P. (S.p.A.), Temi, Italy [22] Filed: Sept. 27, 1971 [2l] Appl. No.: 184,062

[52] US. Cl. 72/57, 72/351 [51] Int. Cl. B21d 26/02 [58] Field of Search 72/57, 351

[56] References Cited UNITED STATES PATENTS 3,566,650 3/1971 Johnson 72/63 l,970,l34 8/1934 Ferris 72/351 3,668,914 6/1972 Voitsekhovsky... 72/57' l,793,054 2/1931 Cams 72/57 2,649,067 8/1953 Kranenberg 72/57 [451 Aug. 14, 1973 Primary Examiner-Richard J. Herbst Att0rney-Allen D. Brufsky 5 7 ABSTRACT A fluid-dynamic press, in particular a hydraulic press, for the cold forming of sheet metal of thin thickness wherein the pressure application means acts directly upon the work piece, comprising a means for providing a packing on the pressure side of the work piece positioned to cooperate with an annular holding plate associated with a plurality of hydraulic clamping pistons on the opposite side of the workpiece, said holding plate and hydraulic clamping pistons being mounted in a removable die body mounted in the press and an integral part of the die. Consequently, the workpiece holding means and sealing means are specifically designed to fit each die body employed.

5 Claims, 2 Drawing Figures FLUID-DYNAMIC PRESS FOR THE COLD FORMING OF SHEET METAL The present invention relates to a fluid-dynamic press for the cold forming of sheet metal, in particular sheets of a very reduced thickness, said press being characterized by the fact that it comprises a forming chamber which is defined by a lower closure wall against which leans the sheet to be formed and through which opens at least one duct connected with a source ofa fluid under pressure, and by a second body, shaped as a box and which is designed to house the die in any suitable removable manner, wherein along the annular area designed to receive and lock up the peripheral edge of the blank during the forming process are provided first means operating between the die edge and that of the closure wall and which are carried by the die and are adapted to perform the locking up of the peripheral edge of the blank, said first means cooperating with packing means adapted to prevent any fluid leakage between said chamber and the outside,- said first means being associated with second means enabling to adjust the locking pressure of the fluid at the different portions of the sheet edge, as well as with third means provided to allow said pressure to be varied during the working cycle.

The machine of this invention is based on an informing principle which differs from that which is applied in the known forming processes, either mechanical or hydraulic, this latter being commonly called hydroform process.

According to the known mechanical forming process, said forming is performed by forcing the metal sheet to take the desired form between a punch and a die.

In the known presses of the hydro-form type,said forming of the sheet is obtained by the combined effect of a fluid under pressure fed into a chamber closed by a flexible diaphragm, against which rests the blank to be formed, and of a piston which acts on the opposite side of said blank, said piston having a head which is shaped according to the form of the workpiece or the like to be obtained.

According to the present invention the punch is eliminated which is always provided in all of the types of the known presses as well as the flexible diaphragm which is used in the presses of the hydro-form type so that the forming of the sheet is carried out under the direct effect of the fluid pressure which directly acts upon one side of the sheet, said pressure causing the deformation of said sheet up to match the form of the inner shaped surface of the die positioned thereupon.

The press of the invention has considerable advantages as compared with the conventional presses in general. In comparison iwth the hydro-form presses with has also the very important advantage that in the press of this invention is eliminated not only. the shaped piston, but also the flexible diaphragm.

Further the press of this invention operates according to a complete cycle; i.e., by a sole forming step a finished workpiece is obtained.

As has hereinabove been stated, in the press of this invention the fluid, which acts as the piston of the conventional presses, is in direct contact with the sheet to be formed and that has as a result to reduce the friction which in the conventional mechanical'presses is produced either between the piston and the sheet, or be tween this latter and the die. Further by the use of the press of thisinvention finished workpieces can be obtained of sized which are largerly wider than those which can be attained with the known machines.

Other advantages of the machine ofthis invention are the following ones:

I. A perfect drawing of the workpieces after a sole forming step, also in the case of workpieces of very elaborate shapes.

2. Possibility of working sheets of very limited thickness up to about 0,4 mm.

3. An easier drawing of the finished workpiece from the machine.

4. A lesser possibility of generating frictions at the end of the operative cycle.

5. Low manufacturing costs.

6. Running pressures lower than those of the conventional presses and as a result thereof, high reduction of the weight of the machine and in consequence thereof lower construction costs.

7. Possibility of working materials which are less ductile than those which can be treated with the conventional presses.

8. Possibility of obtaining sharp-edged workpieces.

9. Possibility of allowing a radial sliding of the material so as to prevent any formation of puckerings, since different values of pressure can be applied in the different zones of the device,said pressure being also gradually varied; in particular they are reduced towards the end of working cycle.

10. The dies are not liable to wear, since the sole area which is subjected to stresses is that where is provided the blank holder.

II. A broad versatility of the machine and a universatility of its use for the working of workpieces of different types, by simply replacing its die;

12. The different treated portions of the sheet maintain their mechanical and physical properties since the material is anywhere stretched during the drawing, thus avoiding any scoring formation thereon.

The press of the invention enables to work a very broad range of articles, for instance, car accessories, as head lamp fittings, escutcheon plates, body portions or the like, as well as parts of household electrical apparatus and appliances, as caps, envelopes, reservoirs or the like; gas cylinders, boxes, containers, reservoirs of various types, trays, convex bottom walls or the like.

The accompanying drawing shows merely by way of indicative example, without limiting the invention an embodiment of this invention, in which:

FIG. 1 shows the press, partly in a vertical sectional view, partly in side view with the partial section of that portion of press where are located the seal locking devices; and

FIG. 2 is a detail in enlarged scale of the left side of FIG. 1.

The press of this invention comprises a bed I carrying the blank holding plate 2, on which will be placed the blank of sheet 3, which will have been previously already suitably sheared. At 4 is marked an upper ram which is made integral with the die 5 in any detachable manner by suitable means not shown in the drawing.

In FIG. 1 a die 5a of another type is also indicated by dotted lines, which can replace the die 5. 6 are the columns provided to guide said upper ram 4, said columns being connected to each other by crosspieces 7 which at their central cross point form a body for supporting the cylinder 8 into which reciprocates a piston, the rod 9 of which is securely fixed to the ram 4 so as to perform the raising or lowering of said ram 4 in order to allow the die to be replaced with another die, the die 50 for instance, having the form suited with the new workpiece to be produced.

During the forming process of a workpiece the upper ram 4 is fixedly connected to the bed 1 by means of a plurality of hydraulic clamping means 10 having clamping heads 10a of a type which is per se known and which therefore are not described in detail. A selected die 5 is mounted in any disconnectable manner into the ram 4 and at its part facing the bed 1 it defines a wide peripheral shoulder 11 into which is inserted an annular body or frame 12 designed to be positioned upon the peripheral edge of the sheet blank 3 so as to constitute the upper holding means for the blank edge. Cooperating with said annular body or frame 12 cylinders 14 are arranged into which are slidably mounted pistons 13 provided to press the blank edge,said cylinders 14 being connected with a source of fluid under pressure by means of a plurality of pipes each associated with a device for varying the fluid pressure and which are not shown in the drawing, since they are well known in the art. By means of said devices the pressure provided to lock the sheet at its different edge points can be varied so as to proportionate said pressure to the stresses acting on the different points according to the particular sheet form to be obtained.

It is also well known that during the drawing process a slipping takes place of the sheet edge at those points where are operative the blank holding means provided to lock the sheet edge.

In consequence thereof the portion of the sheet which is held by said locking means decreases; therefore, if said pressure is maintained constant, as in the conventional similar machines, an increase of the uni tary pressure can be produced which is transmitted to said sheet edge portion up to limits which can also compromise the integrity of the material. For eliminating said inconvenience the present invention provides to associate the means provided to supply the fluid to the piston cylinders 14 with devices adapted to gradually reduce the pressure of the fluid acting on the pistons 13,as the drawing process goes on, said devices being constituted of calibrated exhaust valves or other suitable means which gradually divert a part of the fluid under pressure which is fed to the cylinders 14 in order to evenly reduce the pressure acting on their pistons 13. At 15 is indicated a duct which opens through the plate 2 and which is provided for supplying the fluid under pressure, which according to the present invention, performs the function of the piston of the conventional presses. Into the duct 15 fluid is fed by the conduit 16 which is in turn connected to the pipe 17 conveying the fluid under pressure as well as to an exhaust pipe 18, each of said pipes being controlled by valves not shown in the drawing. At the peripheral portion of the lower blank holding plate 2 which faces the zones where will be positioned the edge 11 of the dies 5,50, etc., and in particular where will act on the plate 2, the upper blank holding unit, grooves 19 are arranged designed to receive seal packing means 20 provided to prevent any leakage of the compressed fluid, which enters through the duct 15 to force the sheet 3 to deform up to match the inner shaped surface of the die 5, through the joint zones between the sheet 3 and the 4 plate 2,said packing means becoming operative owing to the pressure forces transmitted through the edge of the sheet 3 and generated by the upper blank holding means 12,13 and 14 embodied in the die body 5.

The provision that the devices 12 to 14 are embodied into the die body has the advantage that the machine of the invention becomes of an universal performance, since each die 5, 5a etc. is provided with its own blank holding device adapted to act on the edge of a blank 3 of a predetermined shape, each die and the relative blanks to be treated being obviously shaped according to the shape of the piece to be obtained.

I claim:

1. A fluid-dynamic press, in particular a hydraulic press for the cold forming of thin sheet metal, comprising a forming chamber defined by a lower closure wall upon which a blank to be formed is positioned and through which wall passes at least one duct connected with a source of fluid pressure and with an exhaust pipe both controlled by valves and the inner surface of a die housed within a second box-like member in any replaceable manner, said second box-like member and the die inserted therein being provided with peripheral flat lower edges, adjacent said latter edges and that of the closure wall being arranged means adapted to lock the peripheral edge of the blank placed therebetween, said means acting under the effect of a fluid pressure, said locking means operating in combination with packing means designed to prevent any fluid leakage through the joint zones and being associated with second means provided to vary the fluid pressure in the course of the forming process, and with third means adapted to adjust the pressure acting on the different portions of the sheet edge according to the stresses to which said different portions are subjected, wherein the flat lower peripheral edge of the die has a radial width at least equal to that of the peripheral edge portion of the blank to be treated which is designed to be locked between the die edge and that of the closure wall, into said die edge being inserted an annular body or frame, into which are embodied a plurality of hydraulic cylinders or the like having axes substantially set at a right angle to the closure plate, said cylinders communicating by means of a plurality of pipes with a source of pressurized fluid, in said pipes devices are provided for controlling the initial value of the fluid pressure, each of the cylinder pistons acting on the different areas of the edge portions of the blank, as well as further means provided to let said pressure decrease gradually during the forming cycle.

2. A press according to claim 1, wherein the box-like member housing the die is movable in height along guiding members by means adapted to raise and lower it,while the closure wall is constituted of a plate inserted in a bed, means being provided to securely fix the box-like member or ram to said bed in the closure disposition of the forming chamber.

3. A press according to claim 1, wherein along the peripheral portion of said plate inserted in the bed grooves are arranged at that side of it which faces the sheet to be formed, in said grooves being placed packing means.

4. In a fluid-dynamic press for cold forming thin sheet metal workpieces by the direct application of fluid pressure, the improvement comprising, in combination,

a. a replaceable die body having an annular recess adapted to receive pressure application means that act upon the peripheral portion of the thin sheet metal workpiece, said workpiece being inserted into the fluid-dynamic press between the fluid pressure source for the press and the replaceable die means;

b. pressure application means inserted into said annular recess adapted to apply a holding pressure to said workpiece during the forming operation;

c. means in the press body for receiving packing rings eration with said pressure application means to seal the system against fluid leaks, said pressure application means being associated with d. a plurality of hydraulic clamping pistons on the op positc side of the workpiece from said fluid pressure source to permit variations in holding pressure around the periphery of the workpiece.

5. In the apparatus of claim 4 wherein said pressure on the fluid pressure source side of the thin sheet application means is a generally annular body.

metal workpiece which packing rings act in coop- 

1. A fluid-dynamic press, in particular a hydraulic press for the cold forming of thin sheet metal, comprising a forming chamber defined by a lower closure wall upon which a blank to be formed is positioned and through which wall passes at least one duct connected with a source of fluid pressure and with an exhaust pipe both controlled by valves and the inner surface of a die housed within a second box-like member in any replaceable manner, said second box-like member and the die inserted therein being provided with peripheral flat lower edges, adjacent said latter edges and that of the closure wall being arranged means adapted to lock the peripheral edge of the blank placed therebetween, said means acting under the effect of a fluid pressure, said locking means operating in combination with packing means designed to prevent any fluid leakage through the joint zones and being associated with second means provided to vary the fluid pressure in the course of the forming process, and with third means adapted to adjust the pressure acting on the different portions of the sheet edge according to the stresses to which said different portions are subjected, wherein the flat lower peripheral edge of the die has a radial width at least equal to that of the peripheral edge portion of the blank to be treated which is designed to be locked between the die edge and that of the closure wall, into said die edge being inserted an annular body or frame, into which are embodied a plurality of hydraulic cylinders or the like having axes substantially set at a right angle to the closure plate, said cylinders communicating by means of a plurality of pipes with a source of pressurized fluid, in said pipes devices are provided for controlling the initial value of the fluid pressure, each of the cylinder pistons acting on the different areas of the edge portions of the blank, as well as further means provided to let said pressure decrease gradually during the forming cycle.
 2. A press according to claim 1, wherein the box-like member housing the die is movable in height along guiding members by means adapted to raise and lower it,while the closure wall is constituted of a plate inserted in a bed, means being provided to securely fix the box-like member or ram to said bed in the closure disposition of the forming chamber.
 3. A press according to claim 1, wherein along the peripheral portion of said plate inserted in the bed grooves are arranged at that side of it which faces the sheet to be formed, in said grooves being placed packing means.
 4. In a fluid-dynamic press for cold forming thin sheet metal workpieces by the direct application of fluid pressure, the improvement comprising, in combination, a. a replaceable die body having an annular recess adapted to receive pressure application means that act upon the peripheral portion of the thin sheet metal workpiece, said workpiece being inserted into the fluid-dynamic press between the fluid pressure source for the press and the replaceable die means; b. pressure application means inserted into said annular recess adapted to apply a holding pressure to said workpiece during the forming operation; c. means in the press body for receiving packing rings on the fluid pressure source side of the thin sheet metal workpiece which packing rings act in cooperation with said pressure application means to seal the system against fluid leaks, said pressure application means being associated with d. a plurality of hydraulic clamping pistons on the opposite side of the workpiece from said fluid pressure source to permit variations in holding pressure around the periphery of the workpiece.
 5. In the apparatus of claim 4 wherein said pressure application means is a generally annular body. 